When to Clean vs When to Replace Your Pool Filter

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Pool filters need two kinds of care: routine cleaning (weekly to monthly) and eventual replacement (yearly to multi-year). Mixing these up means you either work too hard or let equipment fail. Here's how to tell which one your filter needs.

Cleaning vs replacement — the difference

• Cleaning removes accumulated debris from the filter media so it can keep working. Cartridges get hosed; sand gets backwashed; DE gets flushed and recoated.
• Replacement means the media itself is physically degraded. Pleats are torn, sand is caked, DE grids have holes. No amount of cleaning will restore function.

Cleaning is routine maintenance. Replacement is a cost event you should plan for.

Cartridge filter cleaning

Routine hose cleaning

Every 4-6 weeks during active season, or whenever filter pressure rises 8-10 psi above baseline:

1. Turn pump off, release pressure, remove filter tank top
2. Pull cartridges out (note orientation for reinstallation)
3. Spray each cartridge top-to-bottom with a garden hose, working between pleats
4. Reinstall, button up the tank, prime the pump, restart

Time: 20-30 minutes.

Chemical deep-clean (twice a year)

Soak cartridges overnight in filter cleaner solution (a degreaser + citric acid) to dissolve oils, sunscreen, and mineral buildup that hosing can't reach. Rinse thoroughly before reinstalling.

When to replace cartridges

Typically every 2-3 years. Signs:

• Visible tears, cracks, or collapsed pleats
• Can't get pressure back down to baseline even after chemical cleaning
• End caps loose or separating from pleats
• Pleats flattened and no longer springy
• Fabric has taken on permanent discoloration

Sand filter maintenance

Routine backwashing

When pressure rises 8-10 psi above clean baseline:

1. Turn pump off
2. Move multiport valve to "Backwash"
3. Run pump 2-3 minutes or until sight glass runs clear
4. Turn pump off, switch to "Rinse", run 30 seconds
5. Turn pump off, switch back to "Filter"

Time: 5-10 minutes.

Chemical cleaning (annually)

Once a year, perform a "chemical backwash" using sand filter cleaner to remove oils, scale, and biological buildup the sand traps between grains.

When to replace sand

Typically every 5-7 years. Signs:

• Filter pressure rises faster after each backwash (sand caking)
• Water clarity declining despite proper chemistry
• Backwash water not running clear after extended cycling
• Channels forming in the sand bed (visible if you open the tank)

DE filter maintenance

Routine backwash + recoat

When pressure rises 8-10 psi above baseline:

1. Backwash as with a sand filter
2. After backwash, pump off
3. Mix fresh DE powder with water per filter manual (typically 1 lb per 5 sq ft of grid area)
4. Pour DE slurry into skimmer with pump running to coat grids

Deep clean (annually)

Break down the filter, remove grids, hose off old DE, soak in filter cleaner, inspect grids for damage, reassemble, recoat with fresh DE.

When to replace DE grids

Typically every 5-10 years. Signs:

• DE powder visible in the pool (blowing through torn grids)
• Filter pressure won't rise normally after recoating
• Visible tears or damage to grid fabric
• Grids physically warped

When cleaning won't cut it

Regardless of filter type, these symptoms mean replacement, not cleaning:

• Pressure gauge climbing within days of cleaning
• Water clarity declining even right after service
• Audible leaks or weeping from the filter housing (may be a seal issue, but possibly a cracked tank)
• Visible physical damage to media (tears in cartridges, clumped sand, torn DE grids)

Frequently asked questions

Can I extend cartridge life by running them longer between cleans?

No — letting pressure stay elevated hurts the pump. Clean on pressure schedule, not time.

My backwash runs cloudy forever — what's wrong?

Usually fine sand loss (the bed is old and sand is washing out) or biological growth. Time for sand replacement.

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